1. Field of the Invention
The present invention relates to a circuit arrangement for telecommunication systems, particularly telephone exchange systems, comprising a centralized information processing system and partially-centralized switch devices associated therewith, the switch devices forwarding information, particularly selection information, deriving from different information sources per switch device and, accordingly, consisting of information portions having a limited scope, forwarding the information to an information processing system respectively assigned in common to the switch device and having a limited call handling capability with respect to the information processing capacity. The circuit arrangement further comprises apparatus for determining the information processing traffic load and for the recognition of information processing traffic overloads, and counters provided in the partially-centralized switching devices serving to avert information processing traffic overloads, the counters being incremented on the basis of control signals pertaining to the traffic load and deincremented at regular time intervals according to the information processing capacity and forming an overload signal upon attainment of a limiting value.
2. Description of the Prior Art
A circuit arrangement of the type generally set forth above is disclosed in the German application No. P 32 36 130. Given the arrangement described therein, overload signals are supplied to partially-centralized switching devices which supply information to a centralized information processing device for information processing, the overload signals being supplied thereto by the information processing device when its loadability limit, with respect to traffic loadability, has been exceeded. The counters provided in the partially-centralized switching devices therefore receive overload signals from the centralized information processing device. The overload problem, therefore, lies in the centralized information processing device. Averting overloads is carried out in the partially-centralized switching devices. To this end, the latter receive overload signals from the centralized information processing device. The overload situation, therefore, is identified where it becomes a problem, namely in the centralized information processing device. The German application does not state how this identification of the overload situation occurs, but the same is well known to those skilled in the art.
It was explained in a lecture at the "9.sup.th INTERNATIONAL TELETRAFFIC CONGRESS (ITC)" in October 1979 at Torremolinos, Spain (Conference paper ITC-9 by Somoza et al, pp. 1-7) for the recognition of the overload situation and the formation of overload signals that the number of requests arriving at a centralized computer are counted in individual time segments following successively upon one another and that the tally result thereby obtained each time is compared to a comparitive value; this, moreover, is varied as a function of the respective existing operating situation. Every comparison result provides information regarding the question of the momentary computer traffic load, particularly regarding a potential overload. The number of computer requests and, therefore, the input of information to be processed in the computer can be restricted, or temporarily stopped, entirely on the basis of the traffic load results acquired by counting in each of the time segments and identified by comparison after each conclusion of the counting. The traffic load is thereby to be optimally matched to the call-handling capability and overload limits of the computer in order to achieve as high as possible a utilization of the computer capacity, as well as to avoid, insofar as possible, traffic overloads, these resulting, as known, in considerable, temporary operations, restrictions or operations disruptions for the devices making use of the computer. In the use cases addressed in the lecture, therefore, this is improved by way of a dynamic matching of the traffic load to the computing jobs according to various types and, therein, according to the frequency of the computing jobs supplied to the computer.
The known methods for perceiving and regulating the computer traffic load, however, supply an adequately-precise result only when the individual time interval employed for counting the appertaining events, for example computer requests, is sufficiently large with respect to the mean chronological spacing between these events so that fluctuations in the computer traffic load, the load rising and falling continuously, do not cause the computer traffic load to be represented in course skips, so that a corresponding control is capable of optimally matching the computer traffic load to the loadability. The demand inherent therein, namely that the time interval per individual tally of the events must be sufficiently large, has a negative effect on the respective time at which the results of each of the tally operations are available. The result of identifying the computer traffic load, therefore, still always exhibits a time lag that is necessarily conditioned by the fact that the corresponding result for each acquisition time interval is identified only after the time interval has elapsed, being identified, in particular, by way of a comparison operation. This time lag is, in turn, disadvantageous to influencing the computer traffic load for the purpose of regulating the same. For, namely, either adverting an overload can only take effect when the overload situation has already occurred, i.e. too late in view of actually-arising overloads, or the aversion of an overload must already begin before the overload limit of the computer has been reached, i.e. "under suspension", thus not only in those operating instances in which the computer traffic load, in fact, rises above the loadability limit, rather, in addition, in all of those operating instances as well in which the rise of the computer traffic load in the direction toward the loadability limit only produces the assumption that the loadability limit will be transgressed, but in which the computer traffic load does not, in fact, reach or exceed the loadability limit. The problem therefore lies in the extrapolation of the traffic load behavior over the time. A regulation, however, is less and less effective the later it begins; its relatively late beginning, beyond this, can result in the fact that periods of more pronounced under utilization alternate continuously with periods of overload without this being actually caused by the traffic load that in fact occurs. The demand is further intensified by the condition that the chronological distribution of the events to be acquired varies noticeably, that, therefore, the chronological spacings between the respective successive events are relatively unequal in comparison to one another. This effect is all the more aggravating the smaller the respective acquisition range; the greater the range is, in particular, the greater the influence of the compensating effect of the statistical distribution. This generally testifies in favor of providing the implemented identification of the overload situation at a central location, as can also be derived from the known arrangements. Therefore still remaining as a problem is the early recognition of overload situations, as well as the avoidance of false interruptions of the respective development of the traffic load situation of a centralized information processing system that leads to unnecessary and disadvantageous measures for averting overloads, the call handling capability of the centralized information processing system being disadvantageously constricted by such measures for averting overloads without this actually being necessary as viewed from the traffic load situation.